This invention relates in general to noise reduction structures for use with meshing gear assemblies. In particularly, this invention relates to an improved noise reduction structure for use with a meshing gear assembly in a power take-off unit.
Power take-off units are well known mechanical devices that are commonly used in conjunction with sources of rotational energy, such as vehicle engines and transmissions, for selectively providing power to one or more rotatably driven accessories. For example, power take-off units are commonly used in a variety of industrial and agricultural vehicles for operating hydraulic pumps that, in turn, operate hydraulically driven accessories, such as plows, trash compactors, lifting mechanisms, winches, and the like. The power take-off unit provides a relatively simple and inexpensive mechanism for supplying rotational power from the vehicle engine to operate the rotatably driven accessory.
To accomplish this, a typical power take-off unit includes a rigid housing having a mounting surface formed thereon. An opening is formed through a portion of the mounting surface of the power take-off housing. An input gear is rotatably supported within the housing and includes a portion that extends outwardly through the opening formed through the mounting surface. The mounting surface of the power take-off unit housing is adapted to be secured (typically by a plurality of bolts) to a corresponding mounting surface formed on a case of a transmission provided on the vehicle. An opening is also formed through a portion of the mounting surface of the transmission case. When the power take-off unit housing is secured to the transmission case, the input gear extends through the opening formed through the transmission case into meshing engagement with one of the transmission gears, typically a transmission gear that is driven by the vehicle engine. As a result, the input gear of the power take-off unit is rotatably driven whenever the vehicle engine is operated.
The power take-off unit typically further includes an output gear that is rotatably supported within the housing. The output gear meshes with the input gear such that the output gear is rotatably driven by the input gear whenever the vehicle engine is operated. The output gear is, in turn, connected to an output shaft that is rotatably supported within the power take-off housing. The output shaft extends outwardly from the housing of the power take-off unit and is adapted to be connected to the rotatably driven accessory. In some instances, the output gear is directly connected to the output shaft. In those instances, the output shaft is rotatably driven by the output gear whenever the vehicle engine is operated. In other instances, however, the output gear is connected through a clutch assembly to the output shaft. The clutch assembly is provided within the power take-off housing for selectively connecting the output gear to the output shaft and, therefore, permitting selective or intermittent operation of the rotatably driven accessory whenever the vehicle engine is operated.
When a typical power take-off unit is operated, it often generates an undesirable amount of noise. Such noise usually results from the combination of torsional vibrations that are generated from the vehicle engine to the power take-off unit and backlash or looseness that typically exists between the meshing gears contained within the power take-off unit. It has been found that such torsional vibrations can cause the loosely meshing gears to rattle against one another as they are rotatably driven during use. Although the generation of such noise does not usually adversely affect the operation of the power take-off unit, it can be quite bothersome to persons that are located in the vicinity. A variety of noise reduction structures for meshing gear assemblies are known in the art. However, such known noise reduction structures have been found to be deficient for various reasons. Thus, it would be desirable to provide an improved noise reduction structure for use with a meshing gear assembly in a power take-off unit.